A probe into some Muslim protesters demonstrating in London over cartoons satirising the Prophet Muhammad will be as "swift" as possible, police say.

There have been calls for arrests after placards glorifying the 7 July bombings and calls for the enemies of Islam to be killed featured in Friday's demo.

A team investigating the protests is up and running, Scotland Yard said.

Home Secretary Charles Clarke told the House of Commons action was "quite properly" a matter for police.

Downing Street has said police would have "our full support" in any actions they took.

No protesters were arrested during demonstrations on Friday and Saturday outside the Danish embassy, over the cartoons first printed in a Danish newspaper, but specialist police officers took film and photographic evidence.

'Efficient and thorough'

Scotland Yard has received more than 100 complaints about the protests.

"We are determined that this investigation will be as swift, efficient and thorough as possible, as is reasonable for the crimes committed," a spokesman said.

"Where potential offences have been committed we will pass evidence to the Crown Prosecution Service. We will then take action following their advice and identify offenders who have committed crimes."

The police have our full support in any actions they wish to take where there have been breaches of the law

Mr Clarke said he was pleased that in Britain on the whole the response to the publication of the cartoons had "in general been respectful and restrained in the best traditions of British tolerance."

Prime minister Tony Blair's official spokesman said they understood the offence caused by the cartoons and regretted this had happened, but it did not justify violence seen over the weekend in Syria and Lebanon.

Referring to the demonstrations in London, he said: "We believe some of it was unacceptable but it's up to the police to decide whether to prosecute.

"The police have our full support in any actions they wish to take where there have been breaches of the law - but we should understand the difficult situations they have to manage."

He added: "We welcome the statement here from Muslim leaders condemning the violence."

'Punished and executed'

One protester, who dressed as a suicide bomber, has apologised "wholeheartedly" to the families of the 7 July bombings in London.

I understand it was wrong, unjustified and insensitive of me to protest in this way

Omar Khayam, 22, from Bedford, said it was not his aim to cause offence.

Banned radical cleric Omar Bakri Mohammed, speaking from Beirut, told Radio 4's Today programme that in Islam, whoever insulted a prophet must be "punished and executed".

"We are not saying ourselves to go there and start to look to him and kill him, we are not talking about that. We are talking about Islamic rules. If anybody insults the prophet, he will have to take a punishment," he said.

Shadow home secretary David Davis branded some demonstrators' behaviour incitement to violence, which should not be allowed when "less than a year ago we had over 50 of our citizens killed in a bombing".

Inayat Bunglawala, a spokesman for the Muslim Council of Britain, said there would be "no sympathy" among Muslims for those who waved "incendiary" placards or banners.

"Those extremists who were inciting violence were trying to hijack genuine feelings amongst Muslims for a more violent agenda," he said.

The Archbishop of Westminster Cardinal Cormac Murphy-O'Connor said had been "shocked" by the violent reaction of a small number of Muslims, but he believed faith communities should protest "openly and strongly" when images of their founders were insulted.

Elsewhere, on Monday five people were killed when hundreds clashed with police and soldiers during a demonstration in Afghanistan.

Over the weekend mobs in Syria and Lebanon torched the Danish embassies in Damascus and Beirut.

Among the cartoons which have sparked outcry among Muslims is one of Muhammad with a bomb-shaped turban on his head. Newspapers in Spain, Italy, Germany and France reprinted the material.